1. Field of the Invention
The present invention generally relates to a multi-user multi-antenna system using a closed-loop scheme. More particularly, the present invention relates to a method and apparatus for transmitting/receiving feedback information to support precoding and a system supporting the same.
2. Description of the Related Art
In general, compared to a wired channel, a wireless channel environment has low reliability due to multipath interference, shadowing, propagation attenuation, time-variant noise, and interference. This wireless channel environment is a major obstacle to increasing data rate in mobile communications.
In this context, Multiple Input Multiple Output (MIMO) has been proposed. The MIMO system is a major multi-antenna system.
The multi-antenna system supports both single-user mode and multi-user mode. Data is transmitted to a particular user through a plurality of transmitter antennas in the single-user mode, while data is transmitted to a plurality of users through a plurality of transmitter antennas in the multi-user mode.
Resource allocation in the multi-antenna system is performed by a closed loop using feedback information or an open loop without feedback information. Two types of feedback transmission are considered in a closed-loop multi-antenna system, that is, full feedback and single feedback.
In the full feedback scheme, when precoding is used, each user feeds back all data rates corresponding to all column vectors listed in a codebook. Despite the advantage of excellent performance, the full feedback requires a large amount of feedback information. Consequently, the complexity of creating feedback information increases and more resources are occupied to deliver the feedback information.
In the single feedback scheme, when precoding is used, each user feeds back only the index of a column vector with the highest data rate. Although the single feedback scheme reduces the amount of feedback information, it does not optimize resource allocation.
Efficient resource allocation with minimal feedback information is a significant issue to the closed-loop multi-antenna system. Efficient resource allocation is especially significant for reducing the amount of feedback information when multiple users are supported.
Accordingly, there is a need for an improved method and apparatus for improving system performance without increasing the amount of feedback information in a closed-loop multi-user multi-antenna system.